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Thu, 23 Jan 2020 16:47:52 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1579798076; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=tKmIx2goe/8AH+0OLBD9B3fz9bJTXcfzHsQVtaOAxTc=; b=MKYCy6VpMC4kguFLwHKT9gy2b8Re1bT54CFF0IDb3xkk5ktuo+ArAWNxVaAKAvqcg1juYB huA2MbicSIPF4pPlxRavObxaD4QgytYuweApktpwKQHbkL4jVCjulNVeQdRH0t4T+FfogA vDTUNyyseO0MaY3tMqevSvBjyPjmzHQ= From: "Dr. David Alan Gilbert (git)" To: qemu-devel@nongnu.org, stefanha@redhat.com Subject: [PULL 054/108] virtiofsd: cap-ng helpers Date: Thu, 23 Jan 2020 16:45:36 +0000 Message-Id: <20200123164630.91498-55-dgilbert@redhat.com> In-Reply-To: <20200123164630.91498-1-dgilbert@redhat.com> References: <20200123164630.91498-1-dgilbert@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.84 on 10.5.11.23 X-MC-Unique: eZ9t2gZjO7S9tRk58Z8pYg-1 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Transfer-Encoding: quoted-printable X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] X-Received-From: 205.139.110.61 X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+importer=patchew.org@nongnu.org Sender: "Qemu-devel" X-ZohoMail-DKIM: pass (identity @redhat.com) Content-Type: text/plain; charset="utf-8" From: "Dr. David Alan Gilbert" libcap-ng reads /proc during capng_get_caps_process, and virtiofsd's sandboxing doesn't have /proc mounted; thus we have to do the caps read before we sandbox it and save/restore the state. Signed-off-by: Dr. David Alan Gilbert Reviewed-by: Daniel P. Berrang=C3=A9 Signed-off-by: Dr. David Alan Gilbert --- Makefile | 4 +- tools/virtiofsd/passthrough_ll.c | 72 ++++++++++++++++++++++++++++++++ 2 files changed, 74 insertions(+), 2 deletions(-) diff --git a/Makefile b/Makefile index ad400f36b2..6b4b075a92 100644 --- a/Makefile +++ b/Makefile @@ -327,7 +327,7 @@ HELPERS-y +=3D vhost-user-gpu$(EXESUF) vhost-user-json-y +=3D contrib/vhost-user-gpu/50-qemu-gpu.json endif =20 -ifeq ($(CONFIG_LINUX)$(CONFIG_SECCOMP),yy) +ifeq ($(CONFIG_LINUX)$(CONFIG_SECCOMP)$(CONFIG_LIBCAP_NG),yyy) HELPERS-y +=3D virtiofsd$(EXESUF) vhost-user-json-y +=3D tools/virtiofsd/50-qemu-virtiofsd.json endif @@ -675,7 +675,7 @@ rdmacm-mux$(EXESUF): $(rdmacm-mux-obj-y) $(COMMON_LDADD= S) $(call LINK, $^) =20 # relies on Linux-specific syscalls -ifeq ($(CONFIG_LINUX)$(CONFIG_SECCOMP),yy) +ifeq ($(CONFIG_LINUX)$(CONFIG_SECCOMP)$(CONFIG_LIBCAP_NG),yyy) virtiofsd$(EXESUF): $(virtiofsd-obj-y) libvhost-user.a $(COMMON_LDADDS) $(call LINK, $^) endif diff --git a/tools/virtiofsd/passthrough_ll.c b/tools/virtiofsd/passthrough= _ll.c index bd8925bd83..97e7c75667 100644 --- a/tools/virtiofsd/passthrough_ll.c +++ b/tools/virtiofsd/passthrough_ll.c @@ -39,6 +39,7 @@ #include "fuse_virtio.h" #include "fuse_lowlevel.h" #include +#include #include #include #include @@ -139,6 +140,13 @@ static const struct fuse_opt lo_opts[] =3D { =20 static void unref_inode(struct lo_data *lo, struct lo_inode *inode, uint64= _t n); =20 +static struct { + pthread_mutex_t mutex; + void *saved; +} cap; +/* That we loaded cap-ng in the current thread from the saved */ +static __thread bool cap_loaded =3D 0; + static struct lo_inode *lo_find(struct lo_data *lo, struct stat *st); =20 static int is_dot_or_dotdot(const char *name) @@ -162,6 +170,37 @@ static struct lo_data *lo_data(fuse_req_t req) return (struct lo_data *)fuse_req_userdata(req); } =20 +/* + * Load capng's state from our saved state if the current thread + * hadn't previously been loaded. + * returns 0 on success + */ +static int load_capng(void) +{ + if (!cap_loaded) { + pthread_mutex_lock(&cap.mutex); + capng_restore_state(&cap.saved); + /* + * restore_state free's the saved copy + * so make another. + */ + cap.saved =3D capng_save_state(); + if (!cap.saved) { + fuse_log(FUSE_LOG_ERR, "capng_save_state (thread)\n"); + return -EINVAL; + } + pthread_mutex_unlock(&cap.mutex); + + /* + * We want to use the loaded state for our pid, + * not the original + */ + capng_setpid(syscall(SYS_gettid)); + cap_loaded =3D true; + } + return 0; +} + static void lo_map_init(struct lo_map *map) { map->elems =3D NULL; @@ -2023,6 +2062,35 @@ static void setup_namespaces(struct lo_data *lo, str= uct fuse_session *se) } } =20 +/* + * Capture the capability state, we'll need to restore this for individual + * threads later; see load_capng. + */ +static void setup_capng(void) +{ + /* Note this accesses /proc so has to happen before the sandbox */ + if (capng_get_caps_process()) { + fuse_log(FUSE_LOG_ERR, "capng_get_caps_process\n"); + exit(1); + } + pthread_mutex_init(&cap.mutex, NULL); + pthread_mutex_lock(&cap.mutex); + cap.saved =3D capng_save_state(); + if (!cap.saved) { + fuse_log(FUSE_LOG_ERR, "capng_save_state\n"); + exit(1); + } + pthread_mutex_unlock(&cap.mutex); +} + +static void cleanup_capng(void) +{ + free(cap.saved); + cap.saved =3D NULL; + pthread_mutex_destroy(&cap.mutex); +} + + /* * Make the source directory our root so symlinks cannot escape and no oth= er * files are accessible. Assumes unshare(CLONE_NEWNS) was already called. @@ -2216,12 +2284,16 @@ int main(int argc, char *argv[]) =20 fuse_daemonize(opts.foreground); =20 + /* Must be before sandbox since it wants /proc */ + setup_capng(); + setup_sandbox(&lo, se); =20 /* Block until ctrl+c or fusermount -u */ ret =3D virtio_loop(se); =20 fuse_session_unmount(se); + cleanup_capng(); err_out3: fuse_remove_signal_handlers(se); err_out2: --=20 2.24.1